/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * Copyright (C) 2003-2020 Shaun McCance  <shaunm@gnome.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
 *
 * Author: Shaun McCance  <shaunm@gnome.org>
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <glib.h>
#include <glib/gi18n.h>
#include <glib-object.h>
#include <libxml/parser.h>
#include <libxml/parserInternals.h>
#include <libxml/xinclude.h>
#include <libxml/xpathInternals.h>
#include <libxslt/documents.h>
#include <libxslt/xslt.h>
#include <libexslt/exslt.h>
#include <libxslt/templates.h>
#include <libxslt/transform.h>
#include <libxslt/extensions.h>
#include <libxslt/xsltInternals.h>
#include <libxslt/xsltutils.h>

#include "yelp-debug.h"
#include "yelp-error.h"
#include "yelp-transform.h"

#define YELP_NAMESPACE "http://www.gnome.org/yelp/ns"

static void      yelp_transform_dispose      (GObject                 *object);
static void      yelp_transform_finalize     (GObject                 *object);
static void      yelp_transform_get_property (GObject                 *object,
                                              guint                    prop_id,
                                              GValue                  *value,
                                              GParamSpec              *pspec);
static void      yelp_transform_set_property (GObject                 *object,
                                              guint                    prop_id,
                                              const GValue            *value,
                                              GParamSpec              *pspec);

static void      transform_run              (YelpTransform           *transform);

static gboolean  transform_chunk            (YelpTransform           *transform);
static gboolean  transform_error            (YelpTransform           *transform);
static gboolean  transform_final            (YelpTransform           *transform);

static void      xslt_yelp_document         (xsltTransformContextPtr  ctxt,
                                             xmlNodePtr               node,
                                             xmlNodePtr               inst,
                                             xsltStylePreCompPtr      comp);
static void      xslt_yelp_cache            (xsltTransformContextPtr  ctxt,
                                             xmlNodePtr               node,
                                             xmlNodePtr               inst,
                                             xsltStylePreCompPtr      comp);
static void      xslt_yelp_aux              (xmlXPathParserContextPtr ctxt,
                                             int                      nargs);

enum {
    PROP_0,
    PROP_STYLESHEET
};

enum {
    CHUNK_READY,
    FINISHED,
    ERROR,
    LAST_SIGNAL
};
static gint signals[LAST_SIGNAL] = { 0 };

typedef struct _YelpTransformPrivate YelpTransformPrivate;
struct _YelpTransformPrivate {
    xmlDocPtr                input;
    xmlDocPtr                output;
    gchar                   *stylesheet_file;
    xsltStylesheetPtr        stylesheet;
    xsltTransformContextPtr  context;

    xmlDocPtr                aux;
    xsltDocumentPtr          aux_xslt;

    gchar                 **params;

    GThread                *thread;
    GMutex                  mutex;
    GAsyncQueue            *queue;
    GHashTable             *chunks;

    gboolean                running;
    gboolean                cancelled;

    GError                 *error;
};

G_DEFINE_TYPE_WITH_PRIVATE (YelpTransform, yelp_transform, G_TYPE_OBJECT)

/******************************************************************************/

static void
yelp_transform_init (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);
    priv->queue = g_async_queue_new_full (g_free);
    priv->chunks = g_hash_table_new_full (g_str_hash,
                                          g_str_equal,
                                          g_free,
                                          NULL);
}

static void
yelp_transform_class_init (YelpTransformClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS (klass);

    exsltRegisterAll ();

    object_class->dispose = yelp_transform_dispose;
    object_class->finalize = yelp_transform_finalize;
    object_class->get_property = yelp_transform_get_property;
    object_class->set_property = yelp_transform_set_property;

    signals[CHUNK_READY] = g_signal_new ("chunk-ready",
                                         G_TYPE_FROM_CLASS (klass),
                                         G_SIGNAL_RUN_LAST,
                                         0, NULL, NULL,
                                         g_cclosure_marshal_VOID__STRING,
                                         G_TYPE_NONE, 1, G_TYPE_STRING);
    signals[FINISHED] = g_signal_new ("finished",
                                      G_TYPE_FROM_CLASS (klass),
                                      G_SIGNAL_RUN_LAST,
                                      0, NULL, NULL,
                                      g_cclosure_marshal_VOID__VOID,
                                      G_TYPE_NONE, 0);
    signals[ERROR] = g_signal_new ("error",
                                   G_TYPE_FROM_CLASS (klass),
                                   G_SIGNAL_RUN_LAST,
                                   0, NULL, NULL,
                                   g_cclosure_marshal_VOID__VOID,
                                   G_TYPE_NONE, 0);

    g_object_class_install_property (object_class,
                                     PROP_STYLESHEET,
                                     g_param_spec_string ("stylesheet",
                                                          "XSLT Stylesheet",
                                                          "The location of the XSLT stylesheet",
                                                          NULL,
                                                          G_PARAM_CONSTRUCT_ONLY |
                                                          G_PARAM_READWRITE | G_PARAM_STATIC_NAME |
                                                          G_PARAM_STATIC_NICK | G_PARAM_STATIC_BLURB));
}

static void
yelp_transform_dispose (GObject *object)
{
    YelpTransformPrivate *priv =
        yelp_transform_get_instance_private (YELP_TRANSFORM (object));

    debug_print (DB_FUNCTION, "entering\n");

    if (priv->queue) {
        g_async_queue_unref (priv->queue);
        priv->queue = NULL;
    }

    /* We do not free input or aux.  They belong to the caller, which
       must ensure they exist for the lifetime of the transform.  We
       have to set priv->aux_xslt->doc (which is priv->aux) to NULL
       before xsltFreeTransformContext.  Otherwise it will be freed,
       which we don't want.
     */
    if (priv->aux_xslt)
        priv->aux_xslt->doc = NULL;

    /* We free these in dispose to make absolutely certain that they're
       freed by the time any weak notify callbacks are called.  These
       may be used elsewhere to free resources like the input document.
     */
    if (priv->context) {
        xsltFreeTransformContext (priv->context);
        priv->context = NULL;
    }
    if (priv->stylesheet) {
        xsltFreeStylesheet (priv->stylesheet);
        priv->stylesheet = NULL;
    }
    if (priv->output) {
        xmlFreeDoc (priv->output);
        priv->output = NULL;
    }
    g_clear_pointer (&priv->stylesheet_file, g_free);

    G_OBJECT_CLASS (yelp_transform_parent_class)->dispose (object);
}

static void
yelp_transform_finalize (GObject *object)
{
    YelpTransformPrivate *priv =
        yelp_transform_get_instance_private (YELP_TRANSFORM (object));
    GHashTableIter iter;
    gpointer chunk;

    debug_print (DB_FUNCTION, "entering\n");

    if (priv->error)
        g_error_free (priv->error);

    g_hash_table_iter_init (&iter, priv->chunks);
    while (g_hash_table_iter_next (&iter, NULL, &chunk))
        g_free (chunk);
    g_hash_table_destroy (priv->chunks);

    g_strfreev (priv->params);
    g_mutex_clear (&priv->mutex);

    G_OBJECT_CLASS (yelp_transform_parent_class)->finalize (object);
}

static void
yelp_transform_get_property (GObject    *object,
                             guint       prop_id,
                             GValue     *value,
                             GParamSpec *pspec)
{
    YelpTransformPrivate *priv =
        yelp_transform_get_instance_private (YELP_TRANSFORM (object));

    switch (prop_id)
        {
        case PROP_STYLESHEET:
            g_value_set_string (value, priv->stylesheet_file);
            break;
        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
            break;
    }
}

static void
yelp_transform_set_property (GObject      *object,
                             guint         prop_id,
                             const GValue *value,
                             GParamSpec   *pspec)
{
    YelpTransformPrivate *priv =
        yelp_transform_get_instance_private (YELP_TRANSFORM (object));

    switch (prop_id)
        {
        case PROP_STYLESHEET:
            priv->stylesheet_file = g_value_dup_string (value);
            break;
        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
            break;
    }
}

/******************************************************************************/

YelpTransform *
yelp_transform_new (const gchar *stylesheet)
{
    return (YelpTransform *) g_object_new (YELP_TYPE_TRANSFORM,
                                           "stylesheet", stylesheet,
                                           NULL);
}

gboolean
yelp_transform_start (YelpTransform       *transform,
                      xmlDocPtr            document,
                      xmlDocPtr            auxiliary,
                      const gchar * const *params)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);

    priv->input = document;
    priv->aux = auxiliary;
    priv->params = g_strdupv ((gchar **) params);

    g_mutex_init (&priv->mutex);
    g_mutex_lock (&priv->mutex);
    priv->running = TRUE;
    g_object_ref (transform);
    priv->thread = g_thread_new ("transform-run",
                                 (GThreadFunc)(GCallback) transform_run,
                                 transform);
    g_mutex_unlock (&priv->mutex);

    return TRUE;
}

gchar *
yelp_transform_take_chunk (YelpTransform *transform,
                           const gchar   *chunk_id)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);
    gchar *buf;

    g_mutex_lock (&priv->mutex);

    buf = g_hash_table_lookup (priv->chunks, chunk_id);
    if (buf)
        g_hash_table_remove (priv->chunks, chunk_id);

    g_mutex_unlock (&priv->mutex);

    /* The caller assumes ownership of this memory. */
    return buf;
}

void
yelp_transform_cancel (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);
    g_mutex_lock (&priv->mutex);
    if (priv->running) {
        priv->cancelled = TRUE;
        if (priv->context)
            priv->context->state = XSLT_STATE_STOPPED;
    }
    g_mutex_unlock (&priv->mutex);
}

GError *
yelp_transform_get_error (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);
    GError *ret = NULL;

    g_mutex_lock (&priv->mutex);
    if (priv->error)
        ret = g_error_copy (priv->error);
    g_mutex_unlock (&priv->mutex);

    return ret;
}

/******************************************************************************/

static void
transform_run (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);

    debug_print (DB_FUNCTION, "entering\n");

    priv->stylesheet = xsltParseStylesheetFile (BAD_CAST (priv->stylesheet_file));
    if (priv->stylesheet == NULL) {
        g_mutex_lock (&priv->mutex);
        if (priv->error)
            g_error_free (priv->error);
        priv->error = g_error_new (YELP_ERROR, YELP_ERROR_PROCESSING,
                                   _("The XSLT stylesheet ‘%s’ is either missing or not valid."),
                                   priv->stylesheet_file);
        g_object_ref (transform);
        g_idle_add ((GSourceFunc) transform_error, transform);
        g_mutex_unlock (&priv->mutex);
        return;
    }

    priv->context = xsltNewTransformContext (priv->stylesheet,
                                             priv->input);
    if (priv->context == NULL) {
        g_mutex_lock (&priv->mutex);
        if (priv->error)
            g_error_free (priv->error);
        priv->error = g_error_new (YELP_ERROR, YELP_ERROR_PROCESSING,
                                   _("The XSLT stylesheet ‘%s’ is either missing or not valid."),
                                   priv->stylesheet_file);
        g_object_ref (transform);
        g_idle_add ((GSourceFunc) transform_error, transform);
        g_mutex_unlock (&priv->mutex);
        return;
    }

    priv->context->_private = transform;
    xsltRegisterExtElement (priv->context,
                            BAD_CAST "document",
                            BAD_CAST YELP_NAMESPACE,
                            (xsltTransformFunction) xslt_yelp_document);
    xsltRegisterExtElement (priv->context,
                            BAD_CAST "cache",
                            BAD_CAST YELP_NAMESPACE,
                            (xsltTransformFunction) xslt_yelp_cache);
    xsltRegisterExtFunction (priv->context,
                             BAD_CAST "input",
                             BAD_CAST YELP_NAMESPACE,
                             (xmlXPathFunction) xslt_yelp_aux);

    priv->output = xsltApplyStylesheetUser (priv->stylesheet,
                                            priv->input,
                                            (const char **) priv->params,
                                            NULL, NULL,
                                            priv->context);
    g_mutex_lock (&priv->mutex);
    priv->running = FALSE;
    if (!priv->cancelled) {
        g_idle_add ((GSourceFunc) transform_final, transform);
        g_mutex_unlock (&priv->mutex);
    }
    else {
        g_mutex_unlock (&priv->mutex);
        g_object_unref (transform);
    }
}

static gboolean
transform_chunk (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);
    gchar *chunk_id;

    debug_print (DB_FUNCTION, "entering\n");

    if (priv->cancelled)
        goto done;

    chunk_id = (gchar *) g_async_queue_try_pop (priv->queue);

    g_signal_emit (transform, signals[CHUNK_READY], 0, chunk_id);

    g_free (chunk_id);

 done:
    g_object_unref (transform);
    return FALSE;
}

static gboolean
transform_error (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);

    debug_print (DB_FUNCTION, "entering\n");

    if (priv->cancelled)
        goto done;

    g_signal_emit (transform, signals[ERROR], 0);

 done:
    g_object_unref (transform);
    return FALSE;
}

static gboolean
transform_final (YelpTransform *transform)
{
    YelpTransformPrivate *priv = yelp_transform_get_instance_private (transform);

    debug_print (DB_FUNCTION, "entering\n");

    if (priv->cancelled)
        goto done;

    g_signal_emit (transform, signals[FINISHED], 0);

 done:
    g_object_unref (transform);
    return FALSE;
}

/******************************************************************************/

static void
xslt_yelp_document (xsltTransformContextPtr ctxt,
                    xmlNodePtr              node,
                    xmlNodePtr              inst,
                    xsltStylePreCompPtr     comp)
{
    YelpTransform *transform;
    YelpTransformPrivate *priv;
    xmlChar *page_id = NULL;
    gchar   *temp;
    xmlChar *page_buf;
    gint     buf_size;
    xsltStylesheetPtr style = NULL;
    const char *old_outfile;
    xmlDocPtr   new_doc = NULL;
    xmlDocPtr   old_doc;
    xmlNodePtr  old_insert;

    debug_print (DB_FUNCTION, "entering\n");

    if (!ctxt || !node || !inst || !comp)
        return;

    if (ctxt->state == XSLT_STATE_STOPPED)
        return;

    transform = YELP_TRANSFORM (ctxt->_private);
    priv = yelp_transform_get_instance_private (transform);

    page_id = xsltEvalAttrValueTemplate (ctxt, inst,
                                         (const xmlChar *) "href",
                                         NULL);
    if (page_id == NULL || *page_id == '\0') {
        if (page_id)
            xmlFree (page_id);
        else
            xsltTransformError (ctxt, NULL, inst,
                                _("No href attribute found on "
                                  "yelp:document\n"));
        /* FIXME: put a real error here */
        goto done;
    }
    debug_print (DB_ARG, "  page_id = \"%s\"\n", page_id);

    old_outfile = ctxt->outputFile;
    old_doc     = ctxt->output;
    old_insert  = ctxt->insert;
    ctxt->outputFile = (const char *) page_id;

    style = xsltNewStylesheet ();
    if (style == NULL) {
        xsltTransformError (ctxt, NULL, inst,
                            _("Out of memory"));
        goto done;
    }

    style->omitXmlDeclaration = TRUE;

    new_doc = xmlNewDoc (BAD_CAST "1.0");
    new_doc->charset = XML_CHAR_ENCODING_UTF8;
    new_doc->dict = ctxt->dict;
    xmlDictReference (new_doc->dict);

    ctxt->output = new_doc;
    ctxt->insert = (xmlNodePtr) new_doc;

    xsltApplyOneTemplate (ctxt, node, inst->children, NULL, NULL);
    xsltSaveResultToString (&page_buf, &buf_size, new_doc, style);

    ctxt->outputFile = old_outfile;
    ctxt->output     = old_doc;
    ctxt->insert     = old_insert;

    g_mutex_lock (&priv->mutex);

    temp = g_strdup ((gchar *) page_id);
    xmlFree (page_id);

    g_async_queue_push (priv->queue, g_strdup ((gchar *) temp));
    g_hash_table_insert (priv->chunks, temp, page_buf);

    g_object_ref (transform);
    g_idle_add ((GSourceFunc) transform_chunk, transform);

    g_mutex_unlock (&priv->mutex);

 done:
    if (new_doc)
        xmlFreeDoc (new_doc);
    if (style)
        xsltFreeStylesheet (style);
}

static void
xslt_yelp_cache (xsltTransformContextPtr ctxt,
                 xmlNodePtr              node,
                 xmlNodePtr              inst,
                 xsltStylePreCompPtr     comp)
{
}

static void
xslt_yelp_aux (xmlXPathParserContextPtr ctxt, int nargs)
{
    xsltTransformContextPtr tctxt;
    xmlXPathObjectPtr ret;
    YelpTransform *transform;
    YelpTransformPrivate *priv;

    tctxt = xsltXPathGetTransformContext (ctxt);
    transform = YELP_TRANSFORM (tctxt->_private);
    priv = yelp_transform_get_instance_private (transform);

    priv->aux_xslt = xsltNewDocument (tctxt, priv->aux);

    ret = xmlXPathNewNodeSet (xmlDocGetRootElement (priv->aux));
    xsltExtensionInstructionResultRegister (tctxt, ret);
    valuePush (ctxt, ret);
}